Late Quaternary Paleoceanography of the Mid- to Outer Continental Shelf, East Greenland

Abstract

Cores from a transect along the Kangerdlugssuaq Trough, southeast Greenland shelf, were analyzed for sediment properties, foraminifera, diatoms, opal, and palynomorphs. The transect lies in one of the most climatically sensitive areas in the Northern Hemsiphere, in the path of the outflow of Polar Water from the Arctic Ocean, and in direct proximity of the confluence of Arctic and Atlantic water masses. Mass susceptibility, total organic carbon (TOC), and grain size change markedly around 8 ka, indicating major changes in sediment source and/ or depositional environment and mechanisms. However, this period also marks a major change in sediment accumulation rate associated with the retreat of the ice sheet margin into the fiords. We found that the biogenic and inorganic content of the surface and bottom waters show dramatic changes over the past ca. 14 ka. Surface water changes are indicated by diatoms and opal variations between ca. 13.5 and 9 ka in the form of cool/warm pulses on the outer shelf, where surface water temperature generally declines after 9 ka. On the inner shelf, surface water warming/cooling pulses occur from ca. 9 to 6 ka with a general cooling after ca. 6 ka to present. Dinoflagellates corroborate this interpretation in that they indicate meltwater pulses between 13 and 12 ka on the outer shelf with a warming of surface water around 11 ka. After 6 ka they also suggest a surface water cooling. The 6 ka cooling is also reflected in Baffin Island shelf flora and fauna and is probably caused by a change in Arctic Ocean outflow through the northeastern Canadian archipelago, where the Atlantic Water component was sharply reduced because of isostatic uplift. This change then increased the Arctic Ocean outflow along the East Greenland coast. Transport paths of exotic pollen show marked changes during three time periods, 12–10 ka, 10–8 ka, and 8 ka-present. The changes may show changing intensities of cyclogenesis along the east coast of North America and a deepening of a trough positioned north of the study sites during 12–10 ka and 8 ka to present, making it possible for cyclones to be brought farther into the Arctic.